Bio-efficacy of Herbicides on Performance of Mustard, <Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) and Population Dynamics of Agriculturally Important Bacteria

The bio-efficacy of different herbicide treatments on the performance of mustard crop and its effect on population dynamics of beneficial soil microorganisms like Azotobacter (aerobic and free-living nitrogen fixing bacteria), Bacillus and Pseudomonas (phosphate solubilisation and biocontrol agents) were studied. Higher doses of pendimethalin (@1.0 kg ha^?1) and isoproturon (@1.0 kg ha^?1) had toxic effect on the germination (13.33 and 17.33 m^?2) and emergence of mustard crop and resulted in significantly lower plant population. These treatments resulted in reduction of plant population to the tune of 47.92 and 31.48 % at 30 days after sowing (DAS) and 47.06 and 27.96 % at harvest. Weed free treatment recorded significantly higher seed yield (2781 kg ha^?1) which was about 99 % more than the weedy check. The increase in seed yield with different herbicides was to the tune of 27–73 % over weedy check, except pendimethalin @1.0 kg ha^?1 as pre-emergence (PE). The weedy check plot showed highest population of Azotobacter, Bacillus, and Pseudomonas throughout the observation period. However, among different herbicide treatments, the highest population of Azotobacter and Bacillus was observed with pendimethalin 0.5 kg ha^?1 as PE and that of Pseudomonas with isoproturon 1.0 kg ha^?1 30 DAS at harvest stage.